Self-assembled energetic coordination polymers based on multidentate pentazole cyclo-N_5^-

Coordination to form polymer is emerging as a new technology for modifying or enhancing the properties of the existed energetic substances in energetic materials area. In this work, guanidine cation CN3 H6+ (Gu) and 3-amino-1,2,4-triazole C2H4N4(ATz) were crystallized into NaN5 and two novel energetic coordination polymers(CPs),(NaN5)5[(CH6-N3)N5](N5)3–(1) and(NaN5)2(C2H4N4)(2) were prepared respectively via a self-assembly process. The crystal structure reveals the co-existence of the chelating pentazole anion and organic component in the solid state. In polymer 1, Na+and N5– were coordinated to form a cage structure in which guanidine cation [C(NH2)3]+ was trapped;for polymer 2, a mixedligand system was observed;N5 – and ATz coordinate separately with Na+and form two independent but interweaved nets. In this way, coordination polymer has been successfully utilized to modify specific properties of energetic materials through crystallization. Benefiting from the coordination and weak interactions, the decomposition temperatures of both polymers increase from 111°C(1D structure [Na(H2 O)(N5)]?2 H2 O) to 118.4 and 126.5°C respectively. Moreover, no crystallized H2 O was generated in products to afford the anhydrous compounds of pentazole salts with high heats of formation( >800 kJ mol–1). Compared to traditional energetic materials, the advantage in heats of formation is still obvious for the cyclo-N5– based CPs, which highlights cyclo-N5– as a promising energetic precursor for high energy density materials(HEDMs).

Higher performing and less sensitive CN7^--based high-energy-density material

The highest nitrogen-containing binary C-N anion,5-azido-tetrazolate(CN7^-),has attracted significant attention owing to its high-energy content.Due to its relative instability and high sensitivity,it is an ongoing challenge to develop more stable and less sensitive novel materials based on CN7^-.Towards this goal,we have stabilized the CN7^-anion without compromising its energetic performance by formation of its NH3 OH+salt containing an additional NH2 OH molecule,[NH3 OH][CN7][NH2 OH](2).It possesses the best detonation performance and the lowest mechanical sensitivity among all known CN7^--based materials.The structure-property relationship was elucidated through a careful investigation of the noncovalent interactions in the crystal lattice and the important role of the NH2 OH moiety.In addition,the structurally related compound[NH3 OH][CN7](1)was also studied.